The Sleepless Ape: The Story of Sleep in Human Evolution David R. Samson Princeton Univ. Press (2026) Sleep deprivation disrupts memory: here’s why For millennia, philosophers have argued over why humans sleep and dream. In his fourth-century-bc treatise On Sleep and Sleeplessness, the philosopher Aristotle argued that sleep is a necessary, natural suspension of consciousness that allows the body and soul to recover.